What are the Processes Involved in Compressing Gas?

In a nutshell, whenever any force is applied to pressurise the gas, the process is called compression of gas. It is usually done in industries and factories for different purposes.

Here, we’ll see all the gas compression methods and their work. Primarily, gas compression is done by employing the machines such as bladed rotors, propellers, and pistons. The lesson is vast enough.

Let’s dive into the details. 

Gas compression methods:

There are endless methods of compressing the gas. Some methods which are primarily used are as follows:

• Compress the gas using revolving propellers or bladed rotors, contributing velocity and pressure to the flowing gas. A neighbouring stationary diffuser or blade converts extra velocity energy in the gas to pressure.
• Carry away the gas in a high-velocity jet of another suitable gas, then use a diffuser to turn the mixture’s high velocity to pressure
• Capture large amounts of gas in a container, transport it without changing volume to the release opening, compressing the air by resisting backflow from the discharging line, and force that compressed gas out of the container.
• Capture several quantities of gas in a container, reduce the volume to raise the pressure, and then push the compressed gas out of the container.

Devices used to compress the gas:

Numerous devices are employed to compress the gas. However, devices like Reciprocating pistons, rotatory compressors, and centrifugal compressors are used frequently for commercial purposes.

• Reciprocating piston:

Reciprocating compressors are positive displacement engines featuring a piston that moves in a reciprocating manner inside a cylinder as the compressing and displacing component. Intake, compression, discharge, and expansion are the four basic phases of the total cycle. The drainage ports are open from 2 to 3, and the inlet valves are open from 4 to 1.

• Centrifugal compression.

Centrifugal compressors are dynamical equipment in which a speedily revolving rotor propels the gas. The procedure flow converts velocity to pressure as it moves across axial to radial (perpendicular to the shaft centreline) into a fixed diffuser.

Work Done in Compressing a Gas:

Pressure-volume (PV) work is used to describe the work done during the compression of gases. We can see how the average kinetic energy of the particles grows by watching how the temperature of any gas rises. As the gas particles move faster, they often collide with the pistons. 

These higher-frequency collisions deliver energy to a piston, causing it to advance against an external force, enhancing the gas’s total volume. The gas has acted on the piston’s surroundings and the remainder of the environment in this example.

Moreover, we can conclude that the work is completed by considering two indications. Firstly, as the volume of gas grows and the work done is negative. Otherwise, its volume decreases, and work done is positive.

Formula

W = Px – ΔV

W = Work Done

Px = the external pressure on the gas 

ΔV = the changes in volume. (Difference between the final volume and initial volume)

How much work is needed to compress a specific volume of the gas?

The work needed to compress a specific volume of gas can be evaluated with the formula of work done, which is force multiplied by distance. It can be denoted as W=F dx. Moreover, here, the force applied to the gas should be multiplied by the distance the gas volume has travelled, or say, the difference between the final volume and initial volume.

Conclusion

We learned some of the many essential processes involved in compressing gas from all the above. Some of the most frequently used methods are employing revolving propellers or bladed rotors, using a diffuser and altering its volume after capturing it.

Compressors are used abundantly for industrial and commercial purposes to make it easy. Some machines are Centrifugal compressors, skew compressors, rotatory bladders, and reciprocating pistons.

Moreover, we also came through work done during compression.